Revista chilena de anatomía
versão impressa ISSN 0716-9868
Rev. chil. anat. v.20 n.1 Temuco 2002
LIGHT MICROSCOPICAL STRUCTURE OF THE EFFERENT DUCTULES AND
EPIDIDYMIS IN THE TUFTED CAPUCHIN MONKEYS, Cebus apella
ESTUDIO A TRAVÉS DE MICROSCOPÍA FOTÓNICA DE LA ESTRUCTURA DE LOS
CONDUCTOS EFERENTES Y EPIDÍDIMO DEL MONO, Cebus apella
SUMMARY: The light microscopical structure of the efferent ductuli and epididymis were examined in the tufted capuchin monkeys. The efferent ductules are lined by a simple cuboidal epithelium, with two cell types: ciliated and non-ciliated cells. The epididymal duct is lined by a pseudostratified epithelium with stereocilia, that is made up of four cell types: principal, basal, apical and migratory cells (intraepithelial lymphocytes). Although there are some clear differences, the histological appearance of the excurrent ducts and of the component epithelia of the epididymis, is remarkably similar to that reported for the others mammals.
KEY WORDS: 1. Efferent ductules; 2. Epididymis; 3. Monkey; 4. Light microscopy.
Hamilton (1975) reported that sperm remain in the testicular excurrent duct system for varying periods of time before being ejaculated, and during this time they achieve their full fertilizing capacity, undergoing certain physiological, biochemical, and morphological changes associated with their maturation.
Spermatozoa have little or no fertilizing capacity as they leave the testis but gradually acquire this capacity as they pass through the efferent ductules and epididymis (Hoffer & Greenberg, 1978). Stereological and micro-puncture studies showed that the ductuli efferentes reabsorb most of the fluid leaving the testis (Jones & Jurd, 1987).
The mammalian epididymis is an important segment of the reproductive tract that performs a variety of functions (Abdou et al., 1985). Because of its importance in relation to fluid and sperm resorption, sperm storage and sperm maturation, the epididymis seems to have received more attention than any other segment of the excurrent duct system of the testis (Tingari & Moniem, 1979).
Bedford (1967) and Orgebin-Crist (1967) reported that spermatozoa acquire the ability to swin and fertilize eggs, by passing through epididymis. Hamilton suggest that a sperm is considered fully mature when it can successfully fertilize an ovum and the union results in a viable offspring. This author postulated that statistically it is unlikely that a sperm will be able to do this before it reaches the cauda epididymidis.
There is general agreement that the excurrent ducts are not merely passive conduits for sperm passage, but represent a dynamic system, a fundamental place when sperm attain the ability to fertilize eggs. Thus, the present study describes the histology of the efferent ducts and epididymis of the tufted capuchin monkeys, and compares the findings with previously published data.
MATERIAL AND METHOD
Four adult, sexually mature tufted capuchin monkeys (Cebus apella), after necropsy, had the excurrent ducts dissected from the testis. The tissues representing testis, and morphofunctional regions of the epididymis (initial, middle and terminal) were collected and fixed in Bouin's fluid, dehydrated and embedded in paraffin. Cross sections, 7 µm thickness, were stained with hematoxylin and eosin (H/E), and Mallory's and Masson"s trichromes. The samples were observed in a Olympus BH-2 microscope.
Ductuli efferentes: The ductuli efferentes of the tufted capuchin monkey establish the junction of the rete testis with the epididymal duct. They are very coiled and formes a bulboid structure that is placed in the head of the epididymis, in which the ductuli jumped into the initial segment of the epididymis (Figs. 1 and 2).
Fig. 1. Non-ciliated (nc) and ciliated (arrowheads) cells in the epithelium of the efferentes ductules. x400.
Fig. 2. Photomicrograph showing an abrupt transition in the epithelium at the junction between the efferentes ductules (ed) and initial segment of the epididymis (ep). x200.
The ductuli are lined by a simple cuboidal epithelium. The epithelium lining the ductuli efferentes consists basically of two cell types: ciliated and non-ciliated cells. The non-ciliated cells is the most cell type found in the ductuli and extends from the basal lamina to the lumen of the duct. They could be called principal cells and possess short stereocilia in the luminal border. The ciliated cells is less numerous than the principal cells and is distinguished by the tufts of cilia. The epithelial lining rests on a conspicuous basement membrane that is surrounded by collagen fibrils. Among the ductuli is identified a loose connective tissue (Fig. 1).
As efferent ductules came in close contact with the epididymis, the following junctional changes were noted: a simple columnar ciliated epithelium in the efferent ductules abruptly changed to a tall, pseudostratified columnar epithelium with stereocilia in the epididymis; and an irregular lumen in the efferent ductules changed to a ellongated-shaped lumen in the epididymis (Fig. 2).
Epididymis: The tufted capuchin monkey epididymis was divided into three morphofunctional segments: initial, middle and terminal segments.. The epididymal duct has a similar histological appearance, a epithelium with stereocilia covered with a muscular-connective tissue sheath. The epithelium of the epididymis differs from that of the efferent ductules in that it is pseudostratified columnar. Their height was maximal in the initial segment of the epididymis and become progressively smaller in the middle and terminal segments (Figs. 3, 4, 5 and 6).
Fig. 3. Region of junction between initial and middle segments of the epididymis. Note lumen of the initial segment (star), lumen packed with spermatozoa of the middle segment (l) and stereocilia (s). x200.
Fig. 5. The cell population of the middle segment of the epididymis. Principal (p), basal (b), apical (a) cells and intraepithelial lymphocytes (l) are signalized. x400.
Fig. 6. Distal segment of the epididymis. Stereocilia (s) at the luminal border of the epithelium and spermatozoa (asterisks) in the lumen are shown. x400.
The total membrane surface of the stereocilia is greater in the initial and middle segments (Fig. 3). In the terminal segment of the epididymis, the stereocilia are less abundant and rather short (Fig. 6). The initial segment was characterized by tall and irregular epithelium, which accounted for the elongated appearance of the lumen; lumen of the duct was relatively narrow, and was devoid of spermatozoa (Figs. 2 and 3). In the middle segment, the lumen was still narrow, although regular in form; was spherical in cross section, and densely packed with spermatozoa (Figs. 3 and 4). In general, the major luminal diameter of the epididymal duct was observed in the terminal segment. In this segment, there was a great sperm concentration in the lumen (Fig. 6).
The epididymal epithelia of all segments contained four different cell types: principal, basal, apical and migratory cells. The principal cells was the most numerous cell type of the epithelium. They were tall, cylindrical cell which extend from the basal lamina to the lumen. Their longest axis is perpendicular to the basement membrane. The principal cells possess luminal projections of the apical cell surface, so-called stereocilia, and oval to elongated nuclei (Fig. 5).
The basal cells was second only to the principal cells in number. They rest on the basal lamina, possessed a large ovoid nucleus orientated with its long axis parallel to the basement membrane, and had a high nucleus to cytoplasm ratio. The apical cells possess wide apical portions and narrow stems extending to the basal lamina. Their principal characteristic was apical location of the nucleus. The apical cells are fewer in number than the other cell types reported. The migratory cells consist of intraepithelial lymphocytes which cross the epididymal epithelium of the various regions. They were invariably present near the basal area of the epithelium throughout the length of the epididymis (Fig. 5).
Morphologically, the efferent ductuli and epididymis of tufted capuchin monkey had features in common with other mammals studied, although certain unusual characteristics were observed. The ductuli efferentes were lined by an epithelium of ciliated, and non-ciliated columnar cells similar to those described for the laboratory rat (Hoffer, 1972 and Hamilton), laboratory mouse (Hoffer), guinea pig (Hoffer & Greenberg), plains rats and hopping mice (Peirce & Breed, 1989), and hamster (Flickinger et al., 1978; Vicentini et al., 1990).
A third type of cell, intraepithelial lymphocytes, was observed in the goat efferent ductuli by Goyal et al. (1992). Vicentini et al. have been cited an oval dark cells in the ductuli efferentes of the hamster. These two cell types were not observed in this study. Based on ultrastructural studies, the ciliated cells present basic peculiarities of cells which take part in ciliogenesis (Brenner & Anderson, 1973). The non-ciliated cells participate in the cellular secretion and absorption. The presence of abundant vesicles and vacuoles in the epithelium of the male duct system of the hamster is correlated with sites of fluid absorption (Flickinger et al.). Very large numbers of vesicles and vacuoles were observed in the non-ciliated cells of the epithelium of the efferent ducts, in which physiological studies have indicated that most fluid absorption occurs in the hamster (Jesse & Howards, 1976). Ariyaratna et al. (1996) has been reported in the efferent ductules of the bufallo, the epithelium showed substantial activity with apparent extrusion of enzyme into the lumen. To these authors, this could reflect secretory activity.
The tufted capuchin monkey epididymis has been divided into three morphofunctional segments: initial, middle and terminal segments. The three segments corresponded to the morphofunctional segments originally described by Glover & Nicander (1971) in their subdivisions of the mammalian epididymis. Epididymal epithelial height was maximal in the initial and minimal at the terminal segments. Identical findings were reported in the Rhesus monkey epididymis by Ramos & Dym (1977) and Alsum & Hunter (1978).
The epididymal epithelium of all segments of the tufted capuchin monkey epididymis contains four cell types: principal, basal and apical epithelial cells and migratory cells, as intraepithelial lymphocytes. Goyal & Williams (1991) reported also four cell types in the goat epididymis, although these cell were: principal and basal cells, and intraepithelial lymphocytes and macrophages. In addition, to these authors, only the middle and distal parts of the head and the body of the goat epididymis also contain another cell type, an apical cells.
Basically, the morphology of the epithelial cells in the epididymis of the tufted capuchin monkey appears to be similar to that in the epididymis of the Rhesus monkey (Alsum & Hunter), bull (Goyal, 1985), goat (Goyal & Williams), and dog (Schimming et al., 1997).
The principal cells contain morphological features, such as a well-developed Golgi complex and numerous cisternae of rough endoplasmic reticulum, that are suggestive of their ability to synthesize and secrete proteins/glycoproteins (Hamilton; Goyal; Goyal & Williams). Furthermore, the presence of endocytotic features (microvilli, canaliculi, pinocytotic vesicles, coated vesicles, and subapical vacuoles) and their ability to internalize fluidphase markers (horseradish peroxidase and ferritin) have provided unequivocal evidence for an absorptive function of the principal cells (Djakiew et al., 1984; 1985; Robaire & Hermo, 1988).
According to Hamilton, the basal cells are an enigma. They occur along the epididymal duct of the tufted capuchin monkey, always rest on the basement membrane. Ultrastructural studies showed scattered punctate junctional areas on the interdigitations between principal cells and basal cells, presumably stabilizing the epithelium (Hamilton). In this study, the apical cells were observed, in a few number, along the length of the epididymis. Similarly, a few apical cells have been reported in certain regions of other species of mammals (Hamilton; Ramos & Dym; Hoffer & Greenberg; Goyal, 1985; Goyal & Williams, 1991). Many time, the apical cells are know as mitochondria-rich cells (Goyal & Williams).
Other cell type observed in this report was the presence of intraepithelial lymphocytes. These cell type has been seen in the reproduction tract of rats and Rhesus monkeys (Dym & Romrell, 1975). Wang & Holstein (1983) also described the distribution and morphology of the intraepithelial lymphocytes in the human epididymis. These authors postulated that intraepithelial lymphocytes in the epididymis may be an important component of the immunological barrier of the male reproductive tract.
In addition to the above cell, there is another type, the clear cells, which has been reported in the epididymis of the rat (Hamilton), and hamster (Flickinger et al.). We not observed clear cells in tufted capuchin monkey epididymis. Clear cells are also absent in other species including the guinea pig (Hoffer & Greenberg), bull (Goyal), monkey (Ramos & Dym) and goat (Goyal & Williams).
RESUMEN: Describimos las estructuras de los conductos eferentes y epidídimo en el mono (Cebus apella), usando microscopía de luz. Los conductos eferentes estaban tapizados por un epitelio linear, de tipo cúbico simple y con una población celular que comprendía células ciliadas y no-ciliadas. El epitelio de revestimiento del epidídimo era pseudoestratificado, observándose cuatro tipos de células: principales, basales, apicales y linfocitos. El presente trabajo denota las particularidades del epitelio de los conductos eferentes y epidídimo estableciendo analogías con otras especies de mamíferos.
PALABRAS CLAVE: 1. Conductos eferentes; 2. Epidídimo; 3. Mono; 4. Microscopía de luz.
Abdou, M. S. S.; Moussa, M. H. G.; Ragab, R. S. A. & El Menoufy, A. A. On the regional histology of the ductus epididymis in the buffalo (Bubalus bubalis). Anat. Histol. Embryol., 14:226-35, 1985. [ Links ]
Alsum, D. J. & Hunter, A.G. Regional histology and histochemistry of the ductus epididymis in the Rhesus monkey (Macaca mulatta). Biol. Reprod., 19:1063-9, 1978. [ Links ]
Ariyaratna, H.B.S.; Gunawardana, V. K. & Navaratne, M. A. The epididymis of the prepubertal swamp buffalo (Bubalus bubalis): histochemistry of phosphatases. Anat. Histol. Embryol., 25:161-5, 1996. [ Links ]
Bedford, J. M. Effect of duct ligation on the fertilizing ability of spermatozoa from different regions of the rabbit epididymis. J. Exptl. Zool., 166:271-82, 1967. [ Links ]
Brenner, R.M. & Anderson, R.G.N. Endocrine control of ciliogenesis in the primate oviduct. In: Greep, R.O. & Astwood, E.B. Handbook of Physiology: Female reproductive system. Baltimore: Williams & Wilkins, 1973, p.123-39. [ Links ]
Djakiew, D.; Byers, S.W. & Dym, M. Receptor-mediated endocytosis of alpha-2-macroglobulin and transferrin in rat caput epididymal epithelial cells in vitro. Biol. Reprod., 31: 1073-85, 1984. [ Links ]
Djakiew, D.; Byers, S.W.; Lewis, D. M. & Dym, M. Receptor-mediated endocytosis of alpha-2-macroglobulin by principal cells in the proximal caput epididymidis in vitro. J. Androl., 6:190-6, 1985. [ Links ]
Dym, M. & Romrell, L. J. Intraepithelial lymphocytes in the male reproductive tract of rats and Rhesus monkeys. J. Reprod. Fertil., 42:1-7, 1975. [ Links ]
Flickinger, C.J.; Howards, S.S. & English, H.F. Ultrastructural differences in efferent ducts and several regions of the epididymis of the hamster. Am. J. Anat., 152: 557-86, 1978. [ Links ]
Glover, T. D. & Nicander, L. Some aspects of structure and function in the mammalian epididymis. J. Reprod. Fertil., 13:39-50, 1971. [ Links ]
Goyal, H.O. Morphology of the bovine epididymis. Am. J. Anat., 172:155-72, 1985. [ Links ]
Goyal, H.O. & Williams, C.S. Regional differences in the morphology of the goat epididymis: a light microscope and ultrastructural study. Am. J. Anat., 190:349-69, 1991. [ Links ]
Goyal, H.O.; Hutto, V. & Robinson, D.D. Reexamination of the morphology of the extratesticular rete testis and ductuli efferentes in the goat. Anat. Rec., 233:53-60, 1992. [ Links ]
Hamilton, D.W. Structure and function of the epithelium lining the ductuli efferentes. ductus epididymis and ductus deferens in the rat. In: HAMILTON, D.W. & GREEP, R.O. Handbook of Physiology. Washington D.C.: American Physiological Society, 1975, p. 259-301. [ Links ]
Hoffer, A.P. The fine structure of the ductuli efferentes in mouse and rat. Anat. Rec., 172:331-2, 1972. [ Links ]
Hoffer, A.P. & Greenberg, J. The structure of the epididymis, efferent ductules and ductus deferens of the guinea pig: a light microscope study. Anat. Rec., 190:659-78, 1978. [ Links ]
Jessee, S.J. & Howards, S.S. A survey of sperm, potassium and sodium concentrations in the tubular fluid of the hamster epididymis. Biol. Reprod., 15:626-31, 1976. [ Links ]
Jones, R.C. & Jurd, K.M. Structural differentiation and fluid reabsorption in the ductuli efferentes testis of the rat. Aust. J. Biol. Sci., 40:79-90, 1987. [ Links ]
Orgebin-Crist, M.C. Sperm maturation in the rabbit epididymis. Nature, 216:816-8, 1967. [ Links ]
Peirce, E. J. & Breed, W.G. Light microscopical structure of the excurrent ducts and distribution of spermatozoa in the australian rodents Pseudomys australis and Notomys alexis. J. Anat., 162:195-213, 1989. [ Links ]
Ramos, A.S. & Dym, M. Fine structure of the monkey epididymis. Am. J. Anat., 149:501-32, 1977. [ Links ]
Robaire, B. & Hermo, L. Efferent ducts, epididymis and vas deferens: structure, function and their regulation. In: Knobil, E. & Neill, J.D. The Physiology of Reproduction. New York: Raven Press, 1988, p. 999-1080. [ Links ]
Schimming, B.C.; Vicentini, C.A.; Orsi, A.M.; Franceschini-Vicentini, I. B. & Abreu Rays, M.A. Regional histology of the ductus epididymidis in the dog (Canis familiaris, L.). Rev. Chil. Anat., 15(1):5-12, 1997. [ Links ]
Tingari, M. D. & Moniem, K.A. On the regional histology and histochemistry of the epididymis of the camel (Camelus dromedarius). J. Reprod. Fertil., 57:11-20, 1979. [ Links ]
Vicentini, C. A.; Orsi, A.M. & Gregório, E.A. Fine structure of the ductuli efferentes of the hamster (Mesocricetus auratus). Gegenbaurs morphol. Jahrb., 136:111-8, 1990. [ Links ]
Wang, Y. F. & Holstein, A. F. Intraepithelial lymphocytes and macrophages in the human epididymis. Cell Tissue Res., 233:517-21, 1983. [ Links ]
Prof. Dr. Bruno Cesar Schimming
Department of Anatomy
Faculty of Health Sciences
University of Marília
Av. Hygino Muzzy Filho, 1001
Marília _ São Paulo
Recibido : 28-07-2001
Aceptado : 06-11-2001